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RX-7 1st Gen Specific (1979-85) RX-7 1979-85 Discussion including performance modifications and technical support sections

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Old 06-28-2008, 10:24 PM   #1
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to those that will stick to the nikki...

match the manifold to the engine!

wow thereŽs a HUUUUGE difference in size!

check this pic I took today.

I ported one runner to the engine, the other is stock


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Old 06-29-2008, 09:58 AM   #2
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thats crazy. if i do this will i have to re tune my carb?
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Old 06-29-2008, 12:20 PM   #3
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There are a lot of opinions about this mod.

Some say it causes reversion, others say it kills flow.

Im gonna find out and will tell you later
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Old 06-29-2008, 12:34 PM   #4
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I've seen the same debates, and often wondered who was correct.

In order to truely compare this mod to stock, one would need to test both intakes on the same engine, using the same carb. This testing would require driving the car under many different conditions, as well as dyno testing. There are plenty of things that can 10 HP or more at the dyno, but make an engine much less driveable on the street or track. A few extra HP at the dyno, that kills the real-world performance, isn't worth a hoot.
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Old 06-29-2008, 12:47 PM   #5
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I dont have a dyno avail for free.

But I do have 2 manifolds a carb and a gtech

Plus, I have a very good butt dyno

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Old 06-29-2008, 02:11 PM   #6
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GTech and butt dyno are helpful, but won't tell the full story.

I have my suspictions about what the results will be. Likely going to have negative effects in the lower RPM ranges, that will harm driveability and idle to off-idle throttle response, and have great effects in the upper RPM ranges.
This is based on my theories, not any kind of testing. I *may* see about getting a spare manifold, and testing this for myself. It's something I have been debating for a while.
Of course, the results may be totally different between stockport and streetport engines. They may also vary depending on whether the carb is basiclly stock, or has had the Sterling treatment. Even different exhaust setups could have different results.
In the end, I will be curious to know what you discover. I hope that you will indeed post the results of testing, whether it turns out the way you hope or not.
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Old 06-29-2008, 04:08 PM   #7
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I will
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Old 06-30-2008, 09:42 AM   #8
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I'm using a mani that was ported by someone else, but in a manner similar to what you have done. Seems to me that there is a bit more power, but getting it to idle smoothly is a real challenge. Mine still idles like a V8 with a big cam. Might not be related to the mani, but I've dug into everything else and haven't found any other explanation so far...
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Old 06-30-2008, 03:44 PM   #9
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In theory doing this could adversely affect idle and low-RPM running because of the more pronounced effects of reversion. But does it flow better? I don't know. I tend to trust Paul Yaw's opinion on these matters, and he says it's a bad idea for reasons that make sense to me. But as someone on the other forum pointed out, Yaw's been wrong before.
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Old 06-30-2008, 04:04 PM   #10
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Quote:
Originally Posted by PercentSevenC View Post
But as someone on the other forum pointed out, Yaw's been wrong before.
Hmmmm, I wonder who that coulda been.......
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Old 07-01-2008, 06:20 AM   #11
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so i take it this has been talked about before on the other site and people thought it was a bad idea and a good idea.


"Mine still idles like a V8 with a big cam"
thats how i explain my car.
since i put the racing beat exhaust system on m car. block off plates ect my car ides weird at times. when it hasn't warmed up enough yet my rmp goes up and down and souds like i have a crazy cam in the motor. once it warms up tho it stays at little below 1000k. also when i come off the high way it does it for like 30 secs.
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Old 07-02-2008, 11:54 AM   #12
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If anyone is watching this topic, on that other "forum", you know why I sometimes fail to bother logging in there for 3-5 months at a time.
There are a few "users" there, that I hope never find this place.

Any updates yet? or will it be a while before the engine is ready to run?
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Old 07-02-2008, 11:58 AM   #13
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Quote:
Originally Posted by Rogue_Wulff View Post
If anyone is watching this topic, on that other "forum", you know why I sometimes fail to bother logging in there for 3-5 months at a time.
There are a few "users" there, that I hope never find this place.

Any updates yet? or will it be a while before the engine is ready to run?
IŽm building 2 engines at the same time. (yes, bad idea, but you get dirty ONE time)

One with cermet coated housings. Im almost done on porting the irons for that engine (street port), but I havent started with the housings.

The other one: I ported the housings, but still have to do the half bridge.

whatever engine is build first, will recieve the intake and will be tested against a stock one (not at wot, but idle, etc. After the break in weŽll see)
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Old 07-02-2008, 01:13 PM   #14
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MMMMMM, Cermet housings.......

I know a guy using the cermet housings (SP13B 6p). I want to build a SP12A or 13B 4P using cermet housings. I know the streetport would throw me out of CSP, but it would be worth it. Especially if I add the Camden on my wishlist......

I guess it's gonna be a while before any results are acheived.
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